Our exterior developers have been pretty idle for the last little while -- lead developers aside -- due to the lack of available claims. This isn't much, but it's a start.

The underwater portion of this claim can contain grottos and shipwrecks, including the wreck of an Imperial warship. (Make sure to hide the sails, perhaps by turning the ship upside-down).
Above-ground there should be no obvious dungeons; I'd actually suggest a fisherman's shack or two. An animal den could also work, or perhaps an ancestral tomb. Any smugglers should keep to the western side of the delta, where the channels between the islands are narrower.

Use the attached file, and check the local map; my suggestion is to go with three islands as shown, the two flanking islands detailed to match the islands to the northwest, while the long central island would be a rugged ridge of Ascadian Isles rock sticking out of the water.
You do not have to stick to that configuration, but do try to pay attention to the overall appearance of the delta; the aim is to make it at least appear halfway natural:
http://i.imgur.com/LAqAPOU.png

Other things to watch out for:
-ships should be able to comfortably traverse the delta through at least one channel.
-the islands should not extend too far north of Old Ebonheart; we don't want to shrink the Inner Sea.
-there should be a good reason for there not being a bridge or series of bridges spanning the delta; going by the local map, the reasons would be that the two wide channels are too deep and (though this would not be represented in-game) their waters too swift to make building a bridge convenient, and the islands are of uneven elevations.
-the Hlaalu farmstead in the bottom left cell should be removed, and the corner of land it is on should be submerged/made into an island, as shown in the local map. Its interiors have already been relocated.
-the remaining spur of land in the bottom left of the claim can be beefed up with AI rock and TR_terr_TRV_# meshes to look more solid; it juts into the Thirr creating a choke-point, and might as well look the part.
-ideally, avoid deleting references, the farmstead aside. Underwater assets can be moved to the channels and above-water assets can be moved to the new islands. This both (somewhat) preserves the work of previous modders and greatly speeds up and facilitates progress on the claim, at least in my experience.

Looking very good. I did notice that a lot of the rocks_02 and rocks_04 models were caspering, as they tend to do.

I'm not sure whether we should bother with a formal reviewing process for exteriors at the moment; once you think it's done, I'd certainly be willing to give it a few passes and fix any errors that I find, but as a lot of exterior work and fixing is being done on the section files anyway I'd rather see this merged sooner rather than sitting around in reviewing for a while.